AIRCRAFT

Both aeroplanes and HELICOPTERS are aircraft.
These machines use engines and aerofoil wings to lift off the ground and move
through the air. Aeroplanes use either conventional engines with propellers or
jet engines. Jets burn lots of fuel to generate huge forward thrust and go very
fast. The faster an aeroplane moves, the more lift its wings
produce.

A propeller is a twisted aerofoil, driven by an engine, that spins
around at high speed. As a propeller turns, it generates a backward draft of
air that moves the aeroplane forwards. Aircraft propellers spin faster than
ships’ propellers. This is because aeroplanes need to move forwards more
quickly to generate the lift that keeps them in the air.

AIRLINERS

Airliners can carry hundreds of passengers and huge amounts of
cargo, so they are extremely heavy. They need to have very wide wings to
generate enough lift to overcome the force of gravity and get them into the
air. The huge wings also contain fuel tanks. The liquid fuel is piped directly
to the jet engines under the wings.

HELICOPTERS

This type of aircraft generates lift and thrust using a
huge overhead propeller or rotor. The rotor has several blades shaped like
aerofoils. As the blades spin, they generate lift that overcomes the
helicopter’s weight and lifts it into the air. The pilot can move a
helicopter forwards, backwards, or from side to side by tilting the rotor
blades slightly as they spin around.

HOVERING HELICOPTER

When a helicopter hovers above the ground without moving, the lift
from its rotors is exactly equal and opposite to its weight. Although a normal
aeroplane can fly along at a steady height, it cannot hover. It must move
forwards all the time to generate the lift that keeps it flying.